KR20100016575A - Pre-impregnated composite materials with improved performance - Google Patents

Abstract

Pre-impregnated composite material (prepreg) is provided that can be molded to form composite parts that have high levels of both strength and damage tolerance without causing any substantial negative impact upon the physical or chemical characteristics of the uncured prepreg or cured part. This is achieved by including in the matrix resin a substantial amount of a multifunctional aromatic epoxy resin that has at least one phenyl group that is meta-substituted.

Description

PRE-IMPREGNATED COMPOSITE MATERIALS WITH IMPROVED PERFORMANCE}

The present invention generally relates to pre-impregnated composite materials (prepregs) used to make high performance composite parts. More specifically, the present invention relates to providing a prepreg that can be cured / molded to form composite parts with high strength, damage tolerance.

Detailed description of the related technology

Composite materials typically consist of a continuous resin matrix and reinforcing fibers as two main components. Composite materials are often required to perform operations in demanding environments, such as in the aerospace sector, where the physical limitations and characteristics of composite components are critical. In particular, the tensile strength and modulus of the composite are important factors when determining how lightweight particular composite parts can be manufactured.

Pre-impregnated composite materials (prepregs) are widely used in the manufacture of composite parts. Prepreg is a combination of an uncured resin matrix and a fiber reinforcement, which is a form that is easy to mold and cure into a final composite part. By pre-impregnating the fiber reinforcement with the resin, the manufacturer can carefully control the amount and location of the resin impregnated with the fiber network and allow the resin to be distributed in the network as desired. It is well known that the relative amounts of fibers and resins in composite parts and the distribution of resins in the fiber network have a great influence on the structural properties of the parts. Prepregs are a preferred material for use in the manufacture of load-bearing structural parts and specifically aerospace composite parts such as wings, fuselage, partitions and control surfaces. It is important that these parts have sufficient strength, damage tolerance and other requirements generally established for this.

Fiber reinforcements commonly used in aerospace prepregs are multidirectional fabrics or unidirectional tapes comprising fibers extending parallel to one another. Fibers are typically in the form of numerous individual fibers or filament bundles, referred to as "tows". In addition, fibers or tows can be cut and randomly oriented in the resin to form a nonwoven mat. These various fiber reinforcement arrangements are impregnated with carefully controlled amounts of uncured resin. The resulting prepreg is typically placed between the protective layers and rounded for storage or transportation to a manufacturing facility.

The propreg may also be in the form of short pieces of randomly oriented cut unidirectional tape to form a nonwoven mat of cut unidirectional tape. This type of pre-preg is referred to as a "quasi-isotropic chopped" prepreg. Cut quasi-isotropic prepregs are similar to more traditional nonwoven fiber mat prepregs, except that short lengths of cut unidirectional tape (pieces) are oriented more randomly in the mat than cut fibers.

The tensile strength of the cured composite material is mainly explained by the interaction between these two components, as well as the individual properties of the reinforcing fiber and the matrix resin. In addition, the fiber-resin volume ratio is an important factor. Cured composites under tension tend to fail through the mechanism of cumulative losses resulting from multiple tensile failures of the individual fiber filaments located in the reinforcing tow. If the stress level of the resin adjacent to the broken filament end becomes very large, the entire composite may break. Therefore, the fiber strength near the broken filament end, the strength of the matrix, and the stress dissipation efficiency will contribute to the tensile strength of the cured composite material.

In many applications, it is desirable to maximize the tensile strength properties of the cured composite material. However, attempts to maximize tensile strength often can have negative effects on other desirable properties such as the compressive performance and damage tolerance of the composite structure. In addition, attempts to maximize tensile strength can have unexpected effects on the tack and out-life of the prepreg. Stickiness or tackiness of the uncured prepreg is generally referred to as "tack". The viscosity of uncured prepregs is an important consideration in lay up and molding operations. Prepregs with little or no viscosity are difficult to manufacture with laminates that can be molded to produce structurally strong composite parts. Conversely, prepregs with very high viscosity can be difficult to handle and difficult to position in the mold. The prepreg preferably has an appropriate amount of viscosity to ensure easy handling and good laminate / molding characteristics. In any attempt to increase the strength and / or damage tolerance of a given cured composite material, it is important to keep the viscosity of the uncured prepreg within acceptable limits to ensure proper prepreg handling and molding.

The "out-life" of a prepreg is a period of time during which the prepreg may be exposed to ambient conditions before it becomes unacceptably hardened. The out-life of the prepreg can vary greatly depending on various factors, but is mainly controlled by the resin formulation used. The prepreg out-life should be long enough that routine handling, layup and molding operations are performed without prepreg curing unacceptably. In any attempt to increase the strength and / or damage tolerance of a given cured composite material, the out-life of the uncured prepreg allows sufficient time to treat, handle and lay up the prepreg before curing. It is important to last as long as possible.

The most common way to increase the tensile performance of a composite is to change the surface of the fiber to weaken the strength of the bond between the matrix and the fiber. This can be accomplished by reducing the amount of electro-oxidized surface treatment of the fibers after graphitization. Reducing the matrix fiber bond strength results in a mechanism for stress dissipation at the exposed filament ends by interfacial separation. This interfacial separation increases the amount of tensile loss the composite part can withstand before losing its tensile force.

Alternatively, applying a coating or "size" to the fibers may lower the resin-fiber bond strength. This method is well known in glass fiber composites, but can also be applied to composites reinforced with carbon fiber. By using these strategies, it is possible to increase the tensile strength significantly. However, this improvement entails a reduction in properties such as compression after impact (CAI) strength, which requires a high bond strength between the resin matrix and the fibers.

Another alternative is to use a lower coefficient matrix. Having a low modulus resin reduces the level of stress to be formed in the immediate vicinity of the broken filaments. It usually selects resins (eg cyanate esters) having essentially lower coefficients, or elastomers (carboxy-terminated butadiene-acrylonitrile [CTBN], amine-terminated butadiene-acrylonitrile [ATBN] and the like). Combinations of these various methods are also known.

Choosing a lower modulus resin can be effective to increase composite tensile strength. However, this may result in propensity for damage tolerance typically measured by reduction in compression properties such as post-impact (CAI) strength and open hole compression (OHC) strength. Therefore, it is very difficult to simultaneously increase both tensile strength and damage tolerance.

Existing prepregs are well suited for intentional use to provide strong, damage-tolerant composite parts, but provide prepregs that can be used to manufacture composite parts with higher levels of strength and damage tolerance. It is still necessary. However, this increase in strength and damage tolerance needs to be achieved without adversely affecting the viscosity and out-life of the prepreg as well as other physical properties of the cured composite structure.

Summary of the Invention

According to the present invention, there is provided a pre-impregnated composite material (prepreg) that can be molded to produce composite parts having both high levels of strength and damage tolerance. This is achieved without causing any substantial negative impact on the physical or chemical characteristics of the uncured prepreg or cured composite part.

The pre-impregnated composite material of the present invention consists of reinforcing fibers and a matrix. The matrix comprises a resin component composed of a bifunctional epoxy resin in combination with a polyfunctional aromatic epoxy resin, wherein the multifunctional aromatic epoxy resin has at least one phenyl group which is meta-substituted. The matrix further comprises a thermoplastic particle component, a thermoplastic toughening agent and a curing agent.

The invention also includes a method for producing prepreg and a method for molding the prepreg into various composite parts. The present invention also includes composite parts made using improved prepregs.

It has been found that the selection and combination of components of the present invention form prepregs that can be molded to form composite parts having both improved tensile strength and post-impact compressive (CAI) strength compared to conventional systems. .

In addition, the benefits of improved tensile and CAI strengths can be achieved by prepregs (eg, viscous and out-life) or obtained cured composites (eg, matrix-fiber bonds, strength, stress dissipation, compression performance, etc.). It has surprisingly been found that it can be obtained without substantially affecting other desirable physical properties of c).

Many other features and the accompanying advantages of the invention described above will be better understood with reference to the following detailed description.

The pre-impregnated composite material (prepreg) of the present invention can be used as a replacement for existing prepregs used to manufacture composite parts in the aerospace industry and any other field requiring high structural strength and damage tolerance. Can be. The present invention includes replacing the resin formulation of the present invention instead of the existing resin used to make the prepreg. Thus, the resin formulations of the present invention are suitable for use in any conventional prepreg preparation and curing process.

The pre-impregnated composite material of the present invention consists of reinforcing fibers and an uncured matrix. The reinforcing fibers can be any conventional fiber arrangement used in the prepreg industry. However, the matrix is a departure from conventional prepreg industry practice. The matrix comprises a conventional resin component composed of a bifunctional epoxy resin in combination with at least one multifunctional aromatic epoxy resin having greater than two functionalities. The matrix further comprises a thermoplastic particle component, a thermoplastic toughening agent and a curing agent.

Instead of the para-substituted glycidylamine resins commonly used in aerospace prepreg matrices, the use of epoxy resins having greater than 2 functionality with one or more meta-substituted phenyl rings in their backbones has led to the use of composite materials. It has been found that not only can increase the toughness but also increase the base resin elastic modulus. This causes a gradual change in post-impact compression (CAI) performance. Surprisingly, the matrix resins of the present invention also provide very high tensile strength (eg, open hole tensile strength-OHT) to the composite material.

The bifunctional epoxy resin used to prepare the resin component of the matrix can be any suitable bifunctional epoxy resin. It will be understood to include any suitable epoxy resin with two epoxy functional groups. The bifunctional epoxy resin can be saturated, unsaturated, cycloaliphatic, cycloaliphatic or heterocyclic.

Bifunctional epoxy resins include, for example, those based on the following materials: diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A (optionally brominated), glycidyl ether of phenol-aldehyde adduct , Glycidyl ethers of aliphatic diols, diglycidyl ethers, diethylene glycol diglycidyl ethers, Epikote, Epon, aromatic epoxy resins, epoxidized olefins, brominated resins, aromatic glyces Cydyl amine, heterocyclic glycidyl imine and amide, glycidyl ether, fluorinated epoxy resin, or any combination thereof. The bifunctional epoxy resin is preferably selected from diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A, diglycidyl dihydroxy naphthalene, or a combination thereof. Most preferred is the diglycidyl ether of bisphenol F. The diglycidyl ether of bisphenol F is commercially available from Huntsman Advanced Materials (Brewster, NY) under the trade names Araldite GY281 and GY285. The bifunctional epoxy resin can be used alone or in any suitable combination with other difunctional epoxy.

The bifunctional epoxy resin is present in the range of 10% to 40% by weight of the matrix resin. Preferably, the bifunctional epoxy resin is present in the range of 15% to 35% by weight. More preferably, the bifunctional epoxy resin is present in the range of 22% to 28% by weight.

The second component of the matrix is an epoxy resin having greater than 2 functionality with one or more meta-substituted phenyl rings in its backbone. It will be understood that this includes epoxy resins having epoxy group functionality greater than two. Preferred multifunctional epoxy resins are epoxy resins that are trifunctional or tetrafunctional. Most preferably, the multifunctional epoxy resin is a trifunctional epoxy resin.

Trifunctional epoxy resins will be understood as having three epoxy groups substituted directly or indirectly in a meta orientation on the phenyl ring of the backbone of the compound. Tetrafunctional epoxy resins will be understood as having four epoxy groups substituted either directly or indirectly in meta orientation on the phenyl ring of the backbone of the compound.

It is also contemplated that the phenyl ring may be further substituted with other suitable non-epoxy substituents. Suitable substituents include by way of example hydrogen, hydroxyl, alkyl, alkenyl, alkynyl, alkoxyl, aryl, aryloxyl, aralkyloxyl, aralkyl, halo, nitro, or cyano radicals. Suitable non-epoxy substituents may be bonded to the phenyl ring in the para or ortho position, or in the meta position not occupied by the epoxy group. Suitable tetrafunctional epoxy resins are N, N, N'N'-tetraglycidyl-m-xylenediamine (trade name Tetrad-X), Mitsubishi Gas Chemical Company; Chiyoda-Ku, Commercially available from Tokyo, Japan), and Erisys GA-240 (CVC Chemicals; Morrestown, New Jersey). Suitable trifunctional epoxy resins include, for example, those based on the following materials: bisphenol F, bisphenol A (optionally brominated), phenol and cresol epoxy novolacs; Glycidyl ethers of phenol-aldehyde adducts; Aromatic epoxy resins; Dialiphatic triglycidyl ethers; Aliphatic polyglycidyl ethers; Epoxidized olefins; Brominated resins, aromatic glycidyl amines and glycidyl ethers; Heterocyclic glycidyl imines and amides; Glycidyl ethers; Fluorinated epoxy resins or any combination thereof.

Preferred trifunctional epoxy resins are triglycidyl meta-aminophenols. Triglycidyl meta-aminophenol is commercially available from Huntsman Advanced Materials (Monthey, Swizerland) under the tradename Araldite MY0600 and Sumitomo Chemical Co. (Osaka, Japan) under the tradename ELM-120.

Epoxy resins having greater than 2 functionality with at least one meta-substituted phenyl ring in their backbone are present in the range of 15% to 45% by weight of the resin matrix. Preferably, the meta-substituted epoxy resin is present in the range of 20% to 40% by weight. Most preferred are matrix resins in which the multifunctional meta-substituted epoxy is present in the range from 25% to 30% by weight.

The matrix resin may comprise one or more multifunctional epoxy resins in addition to the required meta-substituted multifunctional epoxy resins. These additional multifunctional epoxy resins are those having at least three epoxy functionalities and having no phenyl ring meta-substituted with an epoxy group in their backbone. Further optional multifunctional epoxy resins may be saturated, unsaturated, cycloaliphatic, cycloaliphatic or heterocyclic.

Suitable further multifunctional epoxy resins include, for example, those based on the following materials: glycidyl ethers of phenol-aldehyde adducts; Aromatic epoxy resins; Dialiphatic triglycidyl ethers, aliphatic polyglycidyl ethers; Epoxidized olefins; Brominated resins; Aromatic glycidyl amines; Heterocyclic glycidyl imines and amides; Glycidyl ethers; Fluorinated epoxy resins or any combination thereof.

Further examples of suitable multifunctional epoxy resins are, for example, Hunts with N, N, N ', N'-tetraglycidyl-4,4'-diaminodiphenyl methane (TGDDM, Araldite MY720 and MY721). Commercially available from Mann Advanced Materials (Monthey, Switzerland) or from Sumitomo with ELM 434, triglycidyl ethers of para aminophenols (commercially available from Huntsman Advanced Materials as Araldite MY 0500 or MY0510) Dicyclopentadiene based epoxy resins, such as Tactix 556 (commercially available from Huntsman Advanced Materials), Tris- (hydroxy phenyl), and Tactix 742 (commercially available from Huntsman Advanced Materials) Methane-based epoxy resins). Other suitable multifunctional epoxy resins include DEN 438 (Dow Chemicals; Midland, MI), DEN 439 (Dow Chemical), Araldite ECN 1273 (Huntsman Advanced Materials), and Araldite ECN 1299 (Huntsman). Advanced Materials).

Said additional multifunctional epoxy resins may be used alone or in any suitable combination. If present, the additional multifunctional epoxy resin (s) should range from 0.1% to 20% by weight of the matrix resin. Preferably, the multifunctional epoxy resin (s) is present in the range of 1% to 15% by weight. More preferably, the multifunctional epoxy resin (s) is present in the range of 5% to 10% by weight.

The prepreg matrix according to the invention also comprises an insoluble thermoplastic particle component. As used herein, the term 'solvable thermoplastic particles' means any suitable material that is thermoplastic, in powder form, sprayed form, or in particle form, and which is present in substantially fine form in the prepreg resin matrix prior to curing. Insoluble thermoplastic particles may undergo some melting if the matrix temperature is increased during curing. However, the particles are substantially reformed and present in particulate form in the final cured matrix.

Insoluble thermoplastic particles are polymers that may be in the form of homopolymers, copolymers, block copolymers, graft copolymers, or terpolymers. The insoluble thermoplastic particles may be thermoplastic resins having a single bond or multiple bonds selected from carbon-carbon bonds, carbon-oxygen bonds, carbon-nitrogen bonds, silicon-oxygen bonds, and carbon-sulfur bonds. One or more repeating units may be present in the polymer which introduce the following moieties into the main polymer backbone or side chains pendant to the main polymer backbone: amide moieties, imide moieties, ester moieties, ether moieties, carbonate moieties, urethane moieties, thioether moieties , Sulfone portion and carbonyl portion. The thermoplastic particles may also have a partially crosslinked structure. The particles can be crystalline or amorphous or partially crystalline.

Suitable examples of insoluble thermoplastic particles include, for example, polyamides, polycarbonates, polyacetals, polyphenylene oxides, polyphenylene sulfides, polyarylates, polyethers, polyesters, polyimides, polyamidoimides, polyether imides, Polysulfones, polyurethanes, polyether sulfones, and polyether ketones.

Insoluble thermoplastic particles can be prepared from polyamide 6 (caprolactam-PA6), polyamide 12 (laurolactam-PA12), polyamide 11, or any combination thereof. Preferred insoluble thermoplastic particles are polyamide particles having a melting point of about 150 ° C to 250 ° C. The particles should have a particle size of less than 100 microns. The average particle size is preferably about 20 microns. Suitable polyamide particles are commercially available from Arkema, France under the trade name Organasol.

Insoluble thermoplastic particle components are present in the range of 35% to 1% by weight of the matrix. Preferably, insoluble thermoplastic particles are present in the range of 20 to 5% by weight. More preferably, insoluble thermoplastic particles are present in the range of 20% to 10% by weight. Very preferably, insoluble thermoplastic particles are present in the range of 10% to 15% by weight of the matrix.

In order to achieve further improvement in damage tolerance (CAI) and open hole tensile strength, some or all of the insoluble thermoplastic particles, preferably polyamide particles, have a melting point below the prepreg curing temperature (typically 180 ° C.), Such low melt particles are preferably used alone or in combination with more molten polyamide particles.

Polyamide particles consist of various grades with different melting temperatures depending on the particular polyamide, degree of copolymerization and degree of crystallinity. Particles mainly containing polyamide 6 (PA6) typically have a melting point higher than 190 ° C., which is much higher than the typical epoxy prepreg curing temperature. Thus, any dissolution of the PA6 particles rarely occurs during curing. Ogazole 1002 D NATl (100% PA6 particles) with a melting point of 217 ° C. (DSC) and a particle size of 20 microns is an example of a high melt polyamide particle. On the other hand, polyamide 12 (PA12) particles and copolymers of PA6 and PA12 have a melting temperature lower than the typical curing temperature for epoxy prepregs. Low melt particles of this type are substantially melted at the curing temperature and reformed into particles as the cured composite cools.

Preferred polyamide particles are PA6 particles and particles which are a copolymer of PA6 and PA12. For example, Ogasol 3502 D NAT 1 is a copolymer of 50% PA12 and 50% PA6 having a melting point of 142 ° C. and an average particle size of about 20 microns. As a further example, development grade organazole CG199 is a copolymer of 80% PA12 and 20% PA6 with a melting point of 160 ° C., with an average particle size of about 20 microns. As another example, 3801 DNAT1 is a copolymer of PA12 and PA6 having a melting point of 160 ° C., a particle size of 20 microns and a molecular weight higher than CG199. The molecular weight of organosol 3801 DANT1 is similar to organosol 1002 DANT1. Organazole CG213 is another preferred copolymer particle containing 80% PA12 and 20% PA6, has a melting point of 160 ° C., a particle size of about 20 microns, and a molecular weight higher than that of organazole CG199. The use of organo CG199 or CG213 on its own is undesirable because CAI decreases despite increasing OHT. Thus, the organosol CG199 or CG213 is preferably combined with high melt polyamide particles.

The polyamide homopolymer and copolymer particles may be included alone or in combination in the matrix. However, a mixture of polyamide particles comprising a high melt polyamide component (ie, a melting temperature higher than the curing temperature for the prepreg) and a low melt polyamide component (ie, a melting temperature lower than the curing temperature for the prepreg) It is preferred to be used. However, the relative amounts of the high melt and low melt particles may vary from case to case. Use of some or all of the low melt polyamide particles (copolymers of PA6 and PA12) results in low modulus without affecting the elastic modulus of the base resin and without compromising the overall water resistance of the composite under humid conditions to the effects of humidity. It has been found possible to achieve an interleave of.

The prepreg matrix resin includes at least one curing agent. Suitable curing agents are those which promote the curing of the epoxy-functional compounds of the invention, in particular those which promote ring opening polymerization of such epoxy compounds. In a particularly preferred embodiment, such curing agents include compounds which polymerize with an epoxy-functional compound or compounds in its ring-opening polymerization. Two or more such curing agents may be used in combination.

Suitable hardeners are anhydrides, in particular polycarboxylic anhydrides such as nadacid anhydride (NA), methylnadic anhydride (available from MNA-Aldrich), phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride (HHPA Anhydrides and Chemicals Inc. (Newark, NJ), methyltetrahydrophthalic anhydride (available from MTHPA-Anhydride and Chemicals Inc), methylhexahydrophthalic anhydride ( Available from MHHPA- Anhydride and Chemicals Inc.), endomethylenetetrahydrophthalic anhydride, hexachloroendomethylene-tetrahydrophthalic anhydride (Velsicol Chemical Corporation; Rosemont, I11.) Available from), trimellitic anhydride, pyromellitic dianhydride, maleic anhydride (MA-Aldrichrobu Available), succinic anhydride (SA), nonenylsuccinic anhydride, dodecenyl succinic anhydride (available from DDSA-Anhydride and Chemicals Inc), polycebacic acid anhydride, and polyazelaic polyanhydride .

Further suitable curing agents include amines including aromatic amines such as 1,3-diaminobenzene, 1,4-diaminobenzene, 4,4'-diaminodiphenylmethane, and polyaminosulfones such as 4, 4'-diaminodiphenyl sulfone (available from 4,4'-DDS-Huntsman), 4-aminophenyl sulfone, and 3,3'-diaminodiphenyl sulfone (3,3'-DDS).

Suitable curing agents also include polyols such as ethylene glycol (available from EG-Aldrich), poly (propylene glycol), and poly (vinyl alcohol); And phenol-formaldehyde resins such as phenol-formaldehyde resins having an average molecular weight of about 550-650, pt-butylphenol-formaldehyde resins having an average molecular weight of about 600-700, and pn- having an average molecular weight of about 1200-1400. Octylphenol-formaldehyde resins (available from Schenectady Chemicals, Inc .; Schenectady, NY) as HRJ 2210, HRJ-2255, and SP-1068, respectively. Further as phenol-formaldehyde resin, a combination of CTU-guanamine, and a phenol-formaldehyde resin having a molecular weight of 398 (commercially available from Ajinomoto USA Inc .; Teaneck, NJ as CG-125) This is also suitable.

Various commercially available compositions can be used as curing agents in the present invention. One such composition is a formulation of the dicyandiamide type as AH-154 and is available from Ajinomoto USA Inc. Other suitable ones include Anamide 18, which is a mixture of polyamide, diethyltriamine, and triethylenetetraamine, aminoamide, imidazoline, and Anamide 18, 506 which are a mixture of tetraethylenepentaamine, and 4,4 '. Ankamid 1284, a mixture of methylenedianiline and 1,3-benzenediamine, these formulations comprising Pacific Ancho Chemical, Performance Chemical Division, Air Products and Chemicals, Air Products and Chemicals, Inc .; Allentown, Pa).

Further suitable curing agents are imidazole (1,3-diaza-2,4-cyclopentadiene) available from Sigma Aldrich (St. Louis, Missouri), 2-ethyl-4- available from Sigma Aldrich Boron trifluoride amine complexes such as Anchor 1170 available from Methylimidazole and Air Products & Chemicals Inc.

Further suitable curing agents are Ajicure, as well as 3,9-bis (3-aminopropyl-2,4,8,10-tetroxaspiro [5.5] undecane, commercially available from Ajinomoto USA Inc. as ATU. ) Aliphatic dehydrazide, also commercially available from Ajinomoto USA Inc. as UDH, and mercapto-terminated polysulfide commercially available from Morton International, Inc .; Chicago, I11 as LP540. .

The curing agent (s), when combined with it at a suitable temperature, are selected to provide curing of the resin component of the composite material. The amount of curing agent needed to provide sufficient curing of the resin component will vary depending on a number of factors including the type of resin to be cured, the desired curing temperature and the curing time. Curing agents typically include cyanoguanidine, aromatic and aliphatic amines, acid anhydrides, Lewis acids, substituted ureas, imidazoles, and hydrazines. The specific amount of curing agent required for each particular situation can be determined by well-established routine experiments.

Exemplary preferred curing agents include 4,4'-diaminodiphenyl sulfone (4,4'-DDS) and 3,3'-diaminodiphenyl sulfone (3,3'-DDS), both of which are Commercially available from Hertzman. Curing agents are present in amounts ranging from 5% to 45% by weight of the uncured matrix. Preferably, the curing agent is present in an amount in the range of 10% to 30% by weight. More preferably, the curing agent is present in the range of 15% to 25% by weight of the uncured matrix. Most preferred are matrix resins containing from 16% to 22% by weight curing agent.

4,4'-DDS is a preferred curing agent. It is preferably used in an amount ranging from 16% to 33% by weight as the sole curing agent. The more reactive 3,3'-DDS will increase the strength of the pure cured resin, but the resulting prepreg is expected to never have as good viscous properties as using the less reactive 4,4'-DDS. Thus, in order to achieve an optimal balance of the mechanical performance of prepreg outlife, viscosity and cured composite parts, less reactive curing agents such as 4,4'-DDS, etc., have a stoichiometric amount of amine to about 70 to 80 percent epoxy. It is preferred to be used in the loan.

The matrix of the invention also preferably comprises a thermoplastic toughening agent. Any suitable thermoplastic polymer can be used as the toughening agent. Typically, the thermoplastic polymer is added to the resin mixture as particles that dissolve in the resin mixture by heating before addition of the curing agent. Once the thermoplastic formulation is sufficiently dissolved in the heated matrix resin precursor (ie the combination of epoxy resin), the precursor is cooled and the remaining components (curing agent and insoluble thermoplastic particles) are added.

Exemplary thermoplastic toughening agents / particles include, alone or in combination with any of the following thermoplastics: polyimide, aramid, polyketone, polyetheretherketone, polyester, polyurethane, polysulfone, polyethersulfone, high performance hydrocarbons Polymers, liquid crystal polymers, PTFE, elastomers and segmented elastomers.

Toughening agents are present in the range of 45% to 5% by weight of the uncured resin matrix. Preferably, the toughening agent is present in the range of 25% to 5% by weight. More preferably, the toughening agent is present in the range of 20% to 10% by weight. Most preferably, the toughening agent is present in the range of 13% to 17% by weight of the matrix resin. By way of example, suitable toughening agents are PES particles sold under the tradename Sumica Excel 5003P, which is commercially available from Sumitomo Chemical. An alternative to 5003P is Solvay polyethersulfone 105PS, or a non-hydroxyl terminated grade such as Solvay 104P.

The matrix resin can also include additional components such as performance enhancers or modifiers and additional thermoplastic polymers, provided they do not negatively affect the viscosity and the tolerability and damage of the prepreg or the outlife or cured composite material. For example, performance enhancers or modifiers may be selected from softening agents, toughening agents / particles, accelerators, core shell rubbers, flame retardants, wetting agents, pigments / dyes, ultraviolet absorbers, antifungal compounds, fillers, conductive particles, and viscosity modifiers. . Suitable further thermoplastic polymers for use as further toughening agents include any of the following materials, alone or in combination: polyether sulfone (PES), polyether ethersulfone (PEES), polyphenyl sulfone, polysulfone, poly Mid, polyetherimide, aramid, polyester, polyketone, polyetheretherketone (PEEK), polyurethane, polyurea, polyarylether, polyarylsulfide, polycarbonate, polyphenylene oxide (PPO) and modified PPO .

Suitable promoters are any urone compounds commonly used. Specific examples of promoters that can be used alone or in combination are N, N-dimethyl, N'-3,4-dichlorophenyl urea (diureon), N'-3-chlorophenyl urea (monurone), and preferably Includes N, N- (4-methyl-m-phenylene bis [N ', N'-dimethylurea] (eg, Dyhard UR500 available from Degussa).

By way of example, suitable fillers include any of the following materials, alone or in combination: silica, alumina, titania, glass, calcium carbonate and calcium oxide.

By way of example, suitable conductive particles include any of the following materials, alone or in combination: silver, gold, copper, aluminum, nickel, conductive grade carbon, buckminsterfullerene, carbon nanotubes and carbon nanofibers. Metal-coated fillers such as nickel coated carbon particles and silver coated copper particles may also be used.

The matrix resin can include additional polymeric resins that are one or more thermosetting resins. The term "thermoset resin" includes any suitable material that is plastic before curing, usually liquid, powder or malleable, and designed to be molded into the final form. Once cured, the thermosetting resin is not suitable for melting and reshaping. Suitable thermosetting resin materials of the present invention are resins of phenol formaldehyde, urea-formaldehyde, 1,3,5-triazine-2,4,6-triamine (melamine), bismaleimide, vinyl ester resin, benzoxazine Resins, phenolic acid resins, polyesters, cyanate ester resins, epoxide polymers, or any combination thereof. Thermosetting resins are preferably selected from epoxide resins, cyanate ester resins, bismaleimides, vinyl esters, benzoxazines and phenolic acid resins. If desired, the matrix may comprise further suitable resins containing phenol groups such as resorcinol based resins, and resins formed by cationic polymerization such as DCPD-phenol copolymers. Further suitable resins are melamine-formaldehyde resins, and urea-formaldehyde resins.

The resin matrix is prepared according to standard prepreg matrix processing. Generally, various epoxy resins are mixed together at room temperature to form a resin mixture, to which a thermoplastic toughening agent is added. This mixture is then heated to a temperature above the melting point of the thermoplastic toughening agent for a time sufficient to substantially melt the toughening agent. The mixture is then cooled to room temperature or below room temperature and the remaining components (if present, insoluble thermoplastic particles, curing agent and other additives) are mixed into the resin to form the final matrix resin that is impregnated with the fiber reinforcement.

The matrix resin is applied to the fiber reinforcement according to any known prepreg manufacturing technique. The fiber reinforcement can be fully or partially impregnated with the matrix resin. In alternative embodiments, the matrix resin can be applied to the fiber reinforcement in a separate layer, which is adjacent and in contact with the fibrous reinforcement but does not substantially impregnate the fiber reinforcement. Prepregs are typically covered on both sides with a protective layer and typically rolled up for storage and transportation at temperatures well maintained below room temperature to prevent premature curing. If desired, any other prepreg manufacturing process and storage / transport system can be used.

The fiber reinforcement of the prepreg can be selected from hybrid or mixed fiber systems comprising synthetic or natural fibers, or combinations thereof. The fiber reinforcement may be preferably selected from any suitable material such as fiber glass, carbon or aramid (aromatic polyamide) fibers. The fiber reinforcement is preferably carbon fiber.

The fiber reinforcement may comprise cracked (ie, stretched-breaked) or optionally discontinuous fibers, or continuous fibers. The use of cracked or optionally discontinuous fibers is expected to facilitate the lay-up of the composite material before it is fully cured and to improve its performance as it is shaped. The fiber reinforcement may be in the form of a woven, non-crimped, nonwoven, unidirectional, or multi-axial fabric structure such as a cut quasi-isotropic prepreg. The fabric form may be selected from plain weave, satin weave, or twill style. Non-critical and multi-axial forms can have multiple ply and fiber orientations. Such styles and shapes are well known in the field of composite stiffeners and are commercially available from a number of companies including Hexel Reinforcements (Villeurbanne, France).

The prepreg can be in the form of a continuous tape, tow preg, web, or cut length (cutting and splitting operations can be carried out at any point after impregnation). The prepreg may be an adhesive or a surfacing film and may additionally have an embedded carrier in various forms of woven, knitted, and nonwoven fabrics. The prepreg may be impregnated completely or only partially, for example to promote air removal upon curing.

Exemplary preferred matrix resins include from about 22% to 25% by weight bisphenol-F diglycidyl ether; About 25-30% triglycidyl- m -aminophenol (trifunctional epoxy resin); About 17-21 weight percent diaminodiphenylsulfone (primarily 4,4-DDS as a hardener); 10 wt% to 15 wt% insoluble thermoplastic particles, and 13 wt% to 17 wt% poly (ether sulfone) as toughening agent.

The prepreg can be molded using any standard technique used to make composite parts. Typically, one or more layers of prepreg are suitably molded and cured to make the final composite part. The prepregs of the present invention can be fully or partially cured using any suitable temperature, pressure, and time conditions known in the art. Typically, the prepreg will cure in the autoclave at a temperature of approximately 180 ° C. The composite material may preferably be cured using a method selected from ultraviolet-visible light, microwaves, electron beams, gamma rays, or other suitable thermal or nonthermal radiation.

Composite parts made from the improved prepregs of the present invention will be found in the manufacture of products such as a number of primary and secondary aerospace structures (wings, fuselage, partitions, etc.), but with high tensile strength, compressive strength, and It will also be useful in many other high performance synthesis applications, including automotive, railroad and marine applications where resistance to impact damage is required.

In order to make the present invention easier to understand, the following background information and examples of the present invention will now be mentioned.

Example 1

Preferred exemplary resin formulations according to the invention are described in Table 1. The epoxy component was mixed with polyethersulfone at room temperature to form a resin blend which was heated to 120 ° C. for 120 minutes to completely dissolve the polyethersulfone to prepare a matrix resin. The mixture was cooled to 80 ° C. and mixed thoroughly by addition of the rest of the ingredients.

TABLE 1

Exemplary prepregs were prepared by impregnating one or more layers of unidirectional carbon fiber into the resin formulation of Table 1. Unidirectional carbon fibers were used to prepare prepregs with a matrix resin of 35% by weight of the total weight of the uncured prepreg, with a fiber area weight of 268 grams per square meter (gsm). Various prepreg lay-ups were made using standard prepreg manufacturing procedures. The prepreg was cured at 180 ° C. for about 2 hours in an autoclave. The cured prepreg was then performed in a standard test to determine its tensile strength and damage tolerance, as described below.

In-plane shear modulus (IPM) was measured at room temperature using an 8-ply (= + 45 / -45) laminate. The laminate was cured for 2 hours at 180 ° C. in an autoclave and a nominal thickness of 2 mm was obtained. Consolidaton was verified by C-scan. Samples were cut and tested according to the Airbus Test Method AITM 1.0002. The results cited are not standardized.

Post-impact compression (CAI) was measured at 25 Joules using a 16-ply laminate with unidirectional fiber layers oriented quasi-isotropically. The laminate was cured at 180 ° C. for 2 hours in an autoclave. The final laminate thickness was about 4 mm. Cure was verified by C-scan. Samples were cut and tested according to Airbus Test Method AITM 1.0010 (June 2, 1994).

Open hole compression (OHC) was measured at room temperature using a 20-ply laminate with unidirectional layers oriented 40/40/20 during lay-up. The laminate was cured at 180 ° C. for 2 hours in an autoclave and a nominal thickness of 5 mm was obtained. Cure was verified by C-scan. Samples were cut and tested according to Airbus test method AITM 1.0008. The values of the results are normalized to a 60 vol% fraction based on the nominal ply thickness cured by calculations performed according to EN 3784 Method B.

Open hole tensile (OHT) was measured at room temperature using a 20-ply laminate with unidirectional layers oriented 40/40/20 during lay-up. The laminate was cured at 180 ° C. for 2 hours in an autoclave and a nominal thickness of 5 mm was obtained. Cure was verified by C-scan. Samples were cut and tested according to Airbus test method AITM 1.0008. The values of the results are normalized to a 60 vol% fraction based on the nominal ply thickness cured by calculations performed according to EN 3784 Method B.

The cured prepreg had an IPS of about 101 MPa and an IPM of about 5.5 GPa. OHT was about 780 MPa and OHC and CAI were about 370 MPa and 292 MPa, respectively.

Comparative prepreg (C1) was prepared and tested in the same manner as the above-described preferred exemplary prepreg. C1 was identical to the exemplary prepreg except that trifunctional para-glycidyl amine (MY0510) was substituted for trifunctional meta-glycidyl amine (MY0600). The cured prepreg formed had an IPS of about 72 MPa and an IPM of about 5.1 GPa. OHT was about 752 MPa and OHC and CAI were 361 MPa and 227 MPa, respectively.

Comparative Example C1 demonstrates that when trifunctional meta-glycidyl amine epoxy is used in place of trifunctional para-glycidyl amine epoxy, an unexpected significant increase in both tensile strength and damage tolerance occurs. . In addition, this increase in both tensile strength and damage tolerance has been achieved without adversely affecting the outlife of the prepreg and other physical / chemical properties of the viscous or hardened part.

A second comparative prepreg (C2) was prepared in which the matrix contains a combination of trifunctional para-glycidyl amine epoxy resins and tetrafunctional para-glycidyl amine epoxy resins. Specifically, the resin contained: 22.2% by weight GY281 difunctional epoxy; 10.1 wt.% MY0510 (trifunctional para-glycidyl amine epoxy); 21.1 weight% MY721 (tetrafunctional para-glycidyl epoxy); 13.5 wt% organo 1002 particles; 14.0 weight% Sumika Excel 5003P PES; And 19.2 weight% 4,4'-DDS. The C2 prepreg was identical to the other preferred exemplary prepreg above, cured and tested in the same manner. The cured C2 prepreg had an IPS of about 92 MPa and an IPM of about 5.2 GPa. OHT was about 735 MPa and OHC and CAI were 376 MPa and 257 MPa, respectively.

Comparative Example C2 shows that the replacement of a substantial portion of the trifunctional para-glycidyl amine epoxy (MY0510) in C1 with tetrafunctional para-glycidyl amine epoxy (MY721) increases to a certain extent the majority of the properties measured. Explain. However, the degree of increase was not as great as using meta-substituted trifunctional epoxy according to the present invention.

Example 2

Additional exemplary prepregs (A-D) were prepared, cured and tested in the same manner as in Example 1. The prepreg was the same as in Example 1 except that the formulation for the matrix resin was changed. The formulations are described in Table 2 below.

TABLE 2

As can be seen from Table 2, Exemplary Matrix Resin A is the same as in Example 1, except that the curing agent was changed to a combination of 4,4'-DDS and 3,3'-DDS. For Matrix Resin B, the amount of curing agent increased higher than the amount in Example 1 with a corresponding decrease in epoxy resin component. For matrix resins C and D, the amount of curing agent was increased and a combination of 4,4'-DDS and 3,3'-DDS was used.

Test results for cured prepregs using matrix resins A-D are listed in Table 3 below.

TABLE 3

As can be seen from Table 3, the strength and damage tolerance of the cured prepreg vary when different amounts and types of curing agents are used. Both cured prepregs showed a significant increase in both tensile strength and damage tolerance when compared to the C1 prepreg of Example 1. It should be noted that the viscosity and out life characteristics of the prepregs prepared according to this embodiment vary, but are generally acceptable for typical handling, lay-up and curing processes. However, the viscosity and out-life characteristics of the prepreg of Example 1 had greater tolerance. Thus, the amount and combination of curing agents used in Example 1 (ie, substantially all 4,4'-DDS, etc.) is preferred.

Example 3

A further example (3E) of prepreg was prepared according to the present invention. The prepreg included a carbon fiber reinforcement (area weight of 268 grams) similar to the carbon fibers used in the preceding examples, except that different fiber surface treatments were used. Formulations for the matrix resins are shown in Table 4 below. Comparative prepreg C3 was also prepared. Matrix formulations for C3 are also described in Table 4 below.

Table 4

Prepreg laminates were prepared and cured in the same manner as in the previous examples to perform the standard mechanical tests described above for OHT and CAI. The test results are listed in Table 5 below.

Table 5

The results of these examples demonstrate that by using different fiber sizing or fiber coating treatments, the strength and damage tolerance of the cured prepreg can be varied. For example, prepreg C3 was the same as prepreg C2 except using a different coating on carbon fibers. The CAI for C3 was 56 MPa higher than C2, while the OHT of C3 was lower 141 MPa. The use of other surface coatings is also expected to provide similar differences in the strength and damage tolerance of the cured prepreg when the same matrix resin is used.

However, as evidenced by the examples, the present invention relatively increased the strength and damage tolerance of the cured prepreg, regardless of the particular coating or sizing used. For example, the cured prepreg of Example 1 was the same as the cured prepreg of Example 3E except that different coatings were used on the carbon fibers. The cured prepreg of Example 1 had 35 MPa with CAI higher than C2 and 45 MPa with higher OHT. Similarly, the cured prepreg of Example 3E also had 45 MPa with CAI higher than C3 and 83 MPa with higher OHT.

Example 4

Three additional examples of prepreg F-H were prepared according to the present invention. The prepreg contained the same carbon fiber reinforcement (area weight of 268 grams) as the fiber used in Example 3. Formulations for the three matrix resins are shown in Table 6 below.

Table 6

Exemplary prepreg F-H used a low viscosity bisphenol-F epoxy GY285 instead of GY281, a medium viscosity bisphenol-F epoxy. Prepreg F-H also included a mixture of meta-substituted trifunctional epoxy (MY0600) and para-substituted multifunctional epoxy (MY0510 and MY7210). These prepregs were used to prepare laminates tested according to the Boeing test method BMS 8-276, and tensile strength and damage as compared to similar laminates made from prepregs containing no meta-trifunctional epoxy. Tolerance has been demonstrated to increase.

Example 5

Additional exemplary prepregs (I-M) were also prepared, cured, and tested in the same manner as in Example 1. This prepreg was the same as in Example 1 except that the formulation for the matrix resin was varied. The formulations are described in Table 7 below.

TABLE 7

The cured prepreg was treated with the same test procedure as in Example 1. The results are shown in Table 8 below.

Table 8

The exemplary prepreg (I-M) described that several types and combinations of thermoplastic particles can be used in accordance with the present invention to further increase both tensile strength and damage tolerance. Using Ogazole 3502 in combination with Ogazole 1002 (Prepreg J and M) compared to the prepreg of Example 1 using Ogazole 1002 alone, both CAI and OHT of the cured prepreg It is obvious that the increase. In addition, the combination of Ogazole 3502 and Ogazole 1002 provides higher CAI and OHT values than using Ogazole 3502 alone, such as in Prepreg K.

Prepreg L shows the use of Ogazole CG199 instead of Ogazole 1002 has an unexpected effect on OHT. High OHT value 1070 was recorded for the cured prepreg. However, the CAI value 243 was relatively low due to the low particle molecular weight.

According to the present invention, along with other required components, the amount of meta-substituted multifunctional epoxy may be selected from: IPS of at least 70 MPa, as measured according to the standard test procedure described in Example 1; IPM of 4.6 GPa or more; OHC of at least 360 MPA; It should be sufficient to provide a cured prepreg with OHT of at least 790 MPa and CAI of at least 260 MPa.

Therefore, it should be noted by those skilled in the art that the described exemplary embodiments of the invention are merely exemplary within the disclosure and that various other substitutions, adaptations, and variations may be made within the scope of the invention. Accordingly, the invention is not limited by the embodiments described above, but only by the following claims.

Claims (20)

A) reinforcing fibers; And B) a pre-impregnated composite material comprising a matrix, The matrix, a) bifunctional epoxy resins; b) multifunctional aromatic epoxy resins having functionality greater than 2 and having at least one phenyl group which is meta-substituted; c) insoluble thermoplastic particles; d) thermoplastic toughening agents; And e) a pre-impregnated composite material comprising a curing agent. The pre-impregnated composite material of claim 1, wherein the amount of the matrix in the pre-impregnated composite material is from about 25% to about 45% by weight. The pre-impregnated composite material of claim 1, wherein the reinforcing fiber is selected from the group consisting of glass, carbon, and aramid. 3. The pre-impregnated composite material of claim 2, wherein the reinforcing fibers are in the form of woven fabrics, unidirectional fibers, randomly oriented fibers or quasi-isotropic cut unidirectional fiber tape. The bifunctional epoxy resin according to claim 1, wherein the difunctional epoxy resin is selected from the group consisting of diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A, diglycidyl dihydroxy naphthalene and combinations thereof. Pre-impregnated composite materials. The pre-impregnated polyvinyl aromatic resin according to claim 1, wherein the multifunctional aromatic epoxy resin is selected from the group consisting of triglycidyl meta-aminophenol and N, N, N ', N'-tetraglycidyl-m-xylenediamine. Composite materials. The pre-impregnated composite material of claim 1, wherein the thermoplastic component particles essentially comprise polyamide. The method of claim 1, wherein the toughening agent is polyether sulfone, polyether ether sulfone, polyphenyl sulfone, polysulfone, polyimide, polyetherimide, aramid, polyester, polyketone, polyetheretherketone, polyurethane, poly Pre-impregnated composite material selected from the group consisting of urea, polyarylethers, polyarylsulfides, polycarbonates, and polyphenylene oxides. The pre-impregnated composite material of claim 1, wherein the curing agent is an aromatic amine. The method of claim 1 wherein the matrix is 22 to 28% by weight of the bifunctional epoxy resin; 25 to 30% by weight of the multifunctional aromatic epoxy resin; 10-15% by weight of the insoluble thermoplastic particles; 13 to 17 weight percent of the thermoplastic toughening agent; And A pre-impregnated composite material comprising 15 to 17 weight percent of said hardener. A pre-impregnated composite material as defined in claim 10, wherein said multifunctional epoxy resin is triglycidyl-amino-phenolic. 12. The pre-impregnated composite material of claim 11, wherein said bifunctional epoxy resin is diglycidyl ether of bisphenol F. 13. The pre-impregnated composite material of claim 12, wherein said insoluble thermoplastic particles consist essentially of polyamide. The pre-impregnated composite material of claim 13, wherein the thermoplastic toughening agent is polyether sulfone. 15. The pre-impregnated composite material of claim 14, wherein said curing agent is 4,4-diaminodiphenylsulfone. The pre-impregnated composite material of claim 13, wherein the polyamide particles comprise both low melt polyamide particles and high melt polyamide particles. The method of claim 15 wherein the matrix is 22 to 28 weight percent diglycidyl ether of bisphenol F; 25-30% by weight of triglycidyl meta-aminophenol; 10 to 15 weight percent polyamide particles; 13-17 weight percent polyether sulfone; And A pre-impregnated composite material comprising 15 to 17 weight percent 4,4-diaminodiphenylsulfone. A composite part comprising the pre-impregnated composite material according to claim 1, wherein the matrix is cured. A) providing a reinforcing fiber; And B) A method of making a pre-impregnated composite material comprising the step of impregnating said reinforcing fibers with a matrix, wherein The matrix, a) bifunctional epoxy resins; b) multifunctional aromatic epoxy resins having functionality greater than 2 and having at least one phenyl group which is meta-substituted; c) insoluble thermoplastic particles; d) thermoplastic toughening agents; And e) a method of making a pre-impregnated composite material comprising a curing agent. A method of making a composite part, comprising the step of curing the pre-impregnated composite material according to claim 1.